Cosmology Group

Inflation

Cosmological inflation, or inflation for short, is the idea that the early universe underwent an epoch of extremely rapid accelerated expansion. During this area the volume of the universe grew by a factor of ∼1078 within ~10-32 sec. This extremely rapid expansion of the universe ended when the potential energy, driving the rapid exponential expansion, was transferred into radiation which is called reheating.

When inflation was introduced in 1980, its main motivation was to solve the magnetic-monopole problem in the big bang theory, i.e. the question of why we do not see any magnetic monopoles today although they should have been produced at a relatively high rate in the very early universe. One might argue that the monopole problem exists only if there is a grand unified theory, however
inflation provides also a solution to two other classical problems of the big bang scenario: the horizon problem and the flatness problem.
The first one is the question of why the CMB is almost isotropic although (without inflation) the cosmological horizon is composed out of causally disconnected patches. The second one is a fine-tuning issue, i.e. one would need an extremely accurate adjustment of matter density and kinetic energy in the standard expansion after the big band model to arrive at this hardly measurable space curvature as we observe it today.
All these problems are solved by inflation to the extent that due to the huge expansion factor our observable universe today is made out of a very small fraction of the space-time after the big bang.